The invention relates to a fluid control system for the security orientated control of at least one fluid power actuator or actor, comprising at least one local control means for the control of the fluid power actuator by way of control instrumentality means of the fluid control system, at least one sensor being provided for the transfer of at least one information item in relation to at least one operational state of the fluid power system to the local control means.
Furthermore, the invention relates to a fluid control actuator, a local control means for a fluid control system, a software module for a local control means of a fluid system and to a method for the operation of a fluid control system.
One system, of the type to which the invention relates, and termed a xe2x80x9cfluid controlxe2x80x9d system may for example be operated as a pneumatic system with the aid of compressed air or as a hydraulic system with the aid of hydraulic oil as a pressure medium or xe2x80x9cfluidxe2x80x9d. In this case an electrical control means controls, by way of control instrumentality means, as for example valves, the flow of the pressure medium for the operation of the fluid control actuator or actuators. Such an actuator is for example a fluid power cylinder. The respective operational state of the fluid control system is in this case monitored with the aid of a sensor. It may for example be attached to the fluid control actuator of a position sensing system, which provides the control means with information as regards the respective position of the actuator so that same may, on the basis of the information, influence the position of the actuator by suitably acting on it with the pressure medium.
In the case of known fluid control a basic assumption is that by suitable design of the fluid control system it is possible to prevent a security risk occurring within the respective fluid control system. Protection against accidental changes in the condition of, or position in, the fluid control system, as for instance a sudden movement of a piston in a fluid power cylinder owing to a defect of a valve controlling the fluid power cylinder, is however not provided for.
One object of the invention is to provide security functions for fluid control systems.
This object is to be attained by a fluid control system for the security relevant control of at least one fluid control actuator, having at least one local control means for the control of the fluid control actuator by way of control instrumentality means of the fluid control system, there being at least one sensor for the provision of at least one item of information as regards at least one operational state of the fluid control system to the local control means, characterized in that the local control means is so designed that it can evaluate at least one item of information for detecting at least one security relevant state and that, given at least one security relevant state, it implements at least one predetermined consequential action.
The object is furthermore to be attained by a fluid control actuator in accordance with the technical teaching of claim 16, by a control means in accordance with the technical teaching of claim 17, by a software module in accordance with the technical teaching of claim 18 and by a method in accordance with the technical teaching of claim 19.
In this respect the invention is based on the notion of integrating security relevant functions in the fluid control system for the control of the actuator, such functions fulfilling simple and also advanced requirement classes, for instance in accordance with the European standard EN 941-1. The fluid control actuator can for instance be a valve arrangement, a pneumatic drive or a servicing unit. The control instrumentality means may for example comprise a valve arrangement, and be operated by an electronic control module as a local control means. If within the control instrumentality means, the local control means or the controlled fluid control actuator a security relevant, improper function occurs, the local control means will recognize this problem and will initiate consequential action to deal with it.
The local control means ensures that a security relevant state does not pass unrecognized. The monitoring of the security function can then be attuned to the respective fluid control system in a optimum fashion and more particularly to the actuator, which is to be controlled. Sensor instrumentalities, which are in any case present, may then be employed for the security functions as well. It is however also possible that with the aid of some additional sensors even higher security criteria may be attained. Moreover, the fluid control system may be utilized as a complete, compact and prefabricated unit, already having integrated security functions, which for instance may cooperate with a higher order control means. They then do not have to be matched to the locally required security functions in an elaborate manner. The local control means may also transmit and receive messages specially adapted for;the transfer of security relevant information and for the issue of security relevant commands.
The fluid control system in accordance with the invention, which is security orientated, may also be designed as part of a fluid control actuator or actor. Thus for instance the fluid control system may be integrated in a locally controlled valve arrangement, which may be a single valve or a valve group, that is to say a so-called valve island. Furthermore, the security orientated system in accordance with the invention may be a component of a fluid drive, as for example of a pneumatic gripper, a pneumatic cylinder or a pneumatic linear drive. A switch-on valve, a servicing device, as for instance an oiler or a xe2x80x9cpneumatic emergency off meansxe2x80x9d may be controlled by an external or integrated fluid control system in a security orientated manner. Thus in accordance with the invention shut off valves integrated in a pneumatic cylinder may be controlled.
As an example the control means may in accordance with the invention check an information item, as supplied by a sensor for monitoring the movement speed of an actuator, as to whether a predetermined speed of movement of the actuator is being exceeded. In such a case the sensor may even be employed for a plurality of functions, on the one hand for the control of the speed of movement as regards a predetermined value and on the other hand for checking to see whether the actuator has exceeded a security relevant speed of movement.
Further advantageous developments of the invention are defined in the dependent claims.
Once the local control means has detected the existence of a security relevant state, it may for instance cause the fluid control actuator to assume a secure state of operation as a consequential action, such state being for example a so-called xe2x80x9cemergency stopxe2x80x9d function, in the case of which the actuator is halted.
Moreover, the local control means may, for example by way of an LED or a loudspeaker, signalize the presence of the security relevant state and thus facilitate the location of a fault by the operator. Furthermore the local control means may transmit a message concerning the presence of the security relevant state to a higher order control means, if the local control means acts for example as a slave on a bus and is controlled and monitored by the higher order control means functioning as a master. In this case it is also possible for the higher order control means to give an instruction to the local control means for bringing the fluid control actuator into a safe operational state, that is to say for instance the above mentioned xe2x80x9cemergency haltxe2x80x9d function.
In a particularly preferred form of the invention the fluid control system comprises fluid power and/or electrically operated switching off means, which are able to be controlled by the local control means for switching off the effective function of the control instrumentality means as regards the fluid control actuator. The switching off means are for instance check valves placed between the control instrumentality means and the actuator. This means that it is possible for the control instrumentality means to be switched off and therefore decoupled from the actuator, when a fault occurs in the control instrumentality means. Thus for example a valve may leak so that the actuator will assume an irregular, undesired position. The local control means can find such a fault for example using control checking means cooperating with same, as for example pressure sensors, for checking the control instrumentality means.
Moreover, using the switching off means it is possible to cause the local control means firstly to at least partly switch off the effective function of the control instrumentality means by means of the switching off means and then to perform a check of the control instrumentality means. In this case the control instrumentality means may be operated without any undesired influence on the actuator and for example to run through a check cycle. Such a check cycle is for example performed in each case prior to operation of the control instrumentality means so that same are only employed for operation of the actuator, when they function correctly. The control instrumentality means may also be checked cyclically so that any malfunction of the control instrumentality means will be detected, if same as such have been idle for a long period of time.
In accordance with a further possible form of the invention the switching off means are also checked using for example sensors arranged on the switching off means, which detect changes in the state of the switching off means and signalize such information to the local control means. The local control means will then determine whether the signalized changes in state are in accordance with predetermined, expected changes in state or whether a malfunction, which may possibly be security relevant, of the switching off means is involved. The local control means can then signalize this malfunction to, for example, the higher order control means or cause an xe2x80x9cemergency haltxe2x80x9d function to take place. The control means may also perform the check on the switching off means cyclically or in each case after operation of the control instrumentality means or of the switching off means.
The fluid control system can also be instructed by the higher order control means by way of check instruction to check both the switching off means cyclically or in each case for each received check instruction.